PROJECT SUMMARY (See instmctions):, Melanoma is a common and deadly tumor that frequenfiy metastasizes to the central nervous system (CNS), resulting in a median survival durafion of 3.7 month and refractoriness to conventional therapy. A key transcripfionalfactor, signal transducer and activator of transcription (STAT)-3, drives the components of melanoma and is over expressed in 80% of melanoma CNS metastases,. Phosphorylated STAT-3 propagates turhorigenesis by enhancing proliferation, angiogenesis, invasion, metastasis, and mmunosuppression. We developed WP1066, a potent orally administered inhibitor of STAT-3 that displays marked efficacy against established intracerebral melanoma in vivo. The mechanism of WP1066's activity is a combinafion of direct melanoma cytotoxicity and immune cytotoxic clearance. In this proposed study, we will further clarify the mechanisms of activity and targets of WP1066 using murine melanoma models of metastasis to identify biomarkers and potenfial selecfioh criteria for a Phase l/ll cliriical trial. This study will focus on whether over expression of phosphorylated STATS in the parenchymal tumors of patients with stage IV melanoma is predictive of CNS metastasis and whether this over expression is an independent predictor of survival. We have demonstrated that a significant mechanism of WP1066's activity is enhancement of CD8+ T-cell effector resporises and inhibifion of regulatory T cells: Immunotherapy with both interferon-alpha and interieukin-2 is used for melanoma, but the response rates remain low. We will further determine vyhether WP1066 Can markedly improve these immunotherapy modalities in in vivo murine model systems. These studies will lay the groundwork for a potenfial clinical trial of WP1066 as an immunomodulator. These following specific aims are the basis for conducting these studies: 1) Evaluate mechanisms of activity of WP1066 and identify biological markers for a clinical trial of WP1066;2) Evaluate the natural history of p-STAT-3 expression in patients with melanoma and determine whether WP1066 can impact these processes in in vivo murine models to clarify clinical trial design;3) Establish whether reversing immune suppression with WP1066 is synergisfic with other immunotherapies for melanoma. These translational studies will bring to the forefront a novel therapeufic that has real potential to improve the survival of patients with melanoma havirig CNS metastatic disease, a major unmet clinical need.